Half-brother and half-sister

HALF-BROTHER AND HALF-SISTER. Persons who have the same father but different mothers; or the same mother but different fathers.

A Law Dictionary, Adapted to the Constitution and Laws of the United States. By John Bouvier. Published 1856.
References in periodicals archive ?
The allusion is to the extreme possibility of sex with (much) older women, given that Sarah becomes fertile in her old age, and bears a son (Isaac) who is also her nephew, since according to Genesis 20:13, Abraham and Sarah are half-brother and half-sister. Carmichael admits, "Although it was never a possibility that Isaac would have a sexual relationship with Sarah, the lawgiver nonetheless took up the issue of a nephew's relationship to an aunt" (28).